/* ----------------------------------------------------------------------  
* Copyright (C) 2010 ARM Limited. All rights reserved.  
*  
* $Date:        29. November 2010  
* $Revision: 	V1.0.3  
*  
* Project: 	    CMSIS DSP Library  
* Title:	    arm_lms_q15.c  
*  
* Description:	Processing function for the Q15 LMS filter.  
*  
* Target Processor: Cortex-M4/Cortex-M3
*  
* Version 1.0.3 2010/11/29 
*    Re-organized the CMSIS folders and updated documentation.  
*   
* Version 1.0.2 2010/11/11  
*    Documentation updated.   
*  
* Version 1.0.1 2010/10/05   
*    Production release and review comments incorporated.  
*  
* Version 1.0.0 2010/09/20   
*    Production release and review comments incorporated  
*  
* Version 0.0.7  2010/06/10   
*    Misra-C changes done  
* -------------------------------------------------------------------- */ 
 
#include "arm_math.h" 
/**  
 * @ingroup groupFilters  
 */ 
 
/**  
 * @addtogroup LMS  
 * @{  
 */ 
 
 /**  
 * @brief Processing function for Q15 LMS filter.  
 * @param[in] *S points to an instance of the Q15 LMS filter structure.  
 * @param[in] *pSrc points to the block of input data.  
 * @param[in] *pRef points to the block of reference data.  
 * @param[out] *pOut points to the block of output data.  
 * @param[out] *pErr points to the block of error data.  
 * @param[in] blockSize number of samples to process.  
 * @return none.  
 *  
 * \par Scaling and Overflow Behavior:  
 * The function is implemented using a 64-bit internal accumulator.  
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.  
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.  
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.  
 * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.  
 * Lastly, the accumulator is saturated to yield a result in 1.15 format.  
 * 
 * \par 
 * 	In this filter, filter coefficients are updated for each sample and the updation of filter cofficients are saturted. 
 *  
 */ 
 
void arm_lms_q15( 
  const arm_lms_instance_q15 * S, 
  q15_t * pSrc, 
  q15_t * pRef, 
  q15_t * pOut, 
  q15_t * pErr, 
  uint32_t blockSize) 
{ 
  q15_t *pState = S->pState;                     /* State pointer */ 
  uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */ 
  q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */ 
  q15_t *pStateCurnt;                            /* Points to the current sample of the state */ 
  q15_t mu = S->mu;                              /* Adaptive factor */ 
  q15_t *px;                                     /* Temporary pointer for state */ 
  q15_t *pb;                                     /* Temporary pointer for coefficient buffer */ 
  uint32_t tapCnt, blkCnt;                       /* Loop counters */ 
  q63_t acc;                                     /* Accumulator */ 
  q15_t e = 0;                                   /* error of data sample */ 
  q15_t alpha;                                   /* Intermediate constant for taps update */ 
  uint32_t shift = S->postShift + 1u;            /* Shift to be applied to the output */ 
  q31_t coef;                                    /* Teporary variable for coefficient */ 
 
  /* S->pState points to buffer which contains previous frame (numTaps - 1) samples */ 
  /* pStateCurnt points to the location where the new input data should be written */ 
  pStateCurnt = &(S->pState[(numTaps - 1u)]); 
 
  /* Initializing blkCnt with blockSize */ 
  blkCnt = blockSize; 
 
  while(blkCnt > 0u) 
  { 
    /* Copy the new input sample into the state buffer */ 
    *pStateCurnt++ = *pSrc++; 
 
    /* Initialize state pointer */ 
    px = pState; 
 
    /* Initialize coefficient pointer */ 
    pb = pCoeffs; 
 
    /* Set the accumulator to zero */ 
    acc = 0; 
 
    /* Loop unrolling.  Process 4 taps at a time. */ 
    tapCnt = numTaps >> 2u; 
 
    while(tapCnt > 0u) 
    { 
      /* acc +=  b[N] * x[n-N] + b[N-1] * x[n-N-1] */ 
      /* Perform the multiply-accumulate */ 
      acc = __SMLALD(*__SIMD32(px)++, (*__SIMD32(pb)++), acc); 
      acc = __SMLALD(*__SIMD32(px)++, (*__SIMD32(pb)++), acc); 
 
      /* Decrement the loop counter */ 
      tapCnt--; 
    } 
 
    /* If the filter length is not a multiple of 4, compute the remaining filter taps */ 
    tapCnt = numTaps % 0x4u; 
 
    while(tapCnt > 0u) 
    { 
      /* Perform the multiply-accumulate */ 
      acc += (q63_t) (((q31_t) (*px++) * (*pb++))); 
 
      /* Decrement the loop counter */ 
      tapCnt--; 
    } 
 
    /* Converting the result to 1.15 format and saturate the output */ 
    acc = __SSAT((acc >> (16 - shift)), 16); 
 
    /* Store the result from accumulator into the destination buffer. */ 
    *pOut++ = (q15_t) acc; 
 
    /* Compute and store error */ 
    e = *pRef++ - (q15_t) acc; 
 
    *pErr++ = (q15_t) e; 
 
    /* Compute alpha i.e. intermediate constant for taps update */ 
    alpha = (q15_t) (((q31_t) e * (mu)) >> 15); 
 
    /* Initialize state pointer */ 
    /* Advance state pointer by 1 for the next sample */ 
    px = pState++; 
 
    /* Initialize coefficient pointer */ 
    pb = pCoeffs; 
 
    /* Loop unrolling.  Process 4 taps at a time. */ 
    tapCnt = numTaps >> 2u; 
 
    /* Update filter coefficients */ 
    while(tapCnt > 0u) 
    { 
      coef = (q31_t) *pb + (((q31_t) alpha * (*px++)) >> 15); 
      *pb++ = (q15_t) __SSAT((coef), 16); 
      coef = (q31_t) *pb + (((q31_t) alpha * (*px++)) >> 15); 
      *pb++ = (q15_t) __SSAT((coef), 16); 
      coef = (q31_t) *pb + (((q31_t) alpha * (*px++)) >> 15); 
      *pb++ = (q15_t) __SSAT((coef), 16); 
      coef = (q31_t) *pb + (((q31_t) alpha * (*px++)) >> 15); 
      *pb++ = (q15_t) __SSAT((coef), 16); 
 
      /* Decrement the loop counter */ 
      tapCnt--; 
    } 
 
    /* If the filter length is not a multiple of 4, compute the remaining filter taps */ 
    tapCnt = numTaps % 0x4u; 
 
    while(tapCnt > 0u) 
    { 
      /* Perform the multiply-accumulate */ 
      coef = (q31_t) *pb + (((q31_t) alpha * (*px++)) >> 15); 
      *pb++ = (q15_t) __SSAT((coef), 16); 
 
      /* Decrement the loop counter */ 
      tapCnt--; 
    } 
 
    /* Decrement the loop counter */ 
    blkCnt--; 
 
  } 
 
  /* Processing is complete. Now copy the last numTaps - 1 samples to the  
     satrt of the state buffer. This prepares the state buffer for the  
     next function call. */ 
 
  /* Points to the start of the pState buffer */ 
  pStateCurnt = S->pState; 
 
  /* Calculation of count for copying integer writes */ 
  tapCnt = (numTaps - 1u) >> 2; 
 
  while(tapCnt > 0u) 
  { 
 
    *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++; 
    *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++; 
 
    tapCnt--; 
 
  } 
 
  /* Calculation of count for remaining q15_t data */ 
  tapCnt = (numTaps - 1u) % 0x4u; 
 
  /* copy data */ 
  while(tapCnt > 0u) 
  { 
    *pStateCurnt++ = *pState++; 
 
    /* Decrement the loop counter */ 
    tapCnt--; 
  } 
 
} 
 
/**  
   * @} end of LMS group  
   */ 
